Primary electrical training test board apparatus



Aug. 2, 1949. A. E. ROANE 2,477,653

PRIMARY ELECTRICAL TRAINING TEST BOARD APPARATUS Filed Aug. 10; 1943 s Sheets-Sheet 1 IWWMIWMTWMMTWM TI E E 1"%0 1 w 1|] 3 Aura.

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Aug. 2, 1949. A. E. ROANE 2,477,653

PRIMARY ELECTRICAL TRAINING TEST BOARD APPARATUS Filed Aug. 10, 1943 3 Sheets-Sheet 2 Ali-11.31

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0144 ATTORNEY 1949- A. E. ROANE 2,477,653

PRIMARY ELECTRICAL TRAINING TEST BOARD APPARATUS- Filed Aug. 10, 1943 3 Sheets-Sheet 3 E u T AMPERE yous 060%; v IE- .INVENTOR a/MLQ vv Q9; 530G440,

BY Q I ATTOR/Vy Patented Aug. 2, 1949 PRmA RY ELECTRICAL TRAINING TEST BOARD APPARATUS Arden E. Roane, Hagerstown,

Md., assignor to The W. H. Rcisner Manufacturing Company, Inc., Hagerstown, Md., a corporation 01' Maryla Application August 10, 1943, Serial No. 498,118

Claims.

My invention relates broadly to educational apparatus and more particularly to equipment for teaching essentials of the art of electricity and component instrumentalitles used in electrical engineering.

One of the objects of my invention is to provide a construction of connecting means for mounting various electrical components on a test board in such a. manner that electrical connection for such components ma be quickly established or removed and connection of a substitute component reestablished between test terminals.

Another object of my invention is to provide a construction of test apparatus in which the electrical connections may be quickly established in a circuit layout or network and readily replaced by substitute electrical components in the circuit for quick measurement and test.

A still further object of my invention is to provide a construction of expandable or contractible link members for establishing circuit connections between terminal posts of a test board in which the link member is constructed for mounting various forms of electrical components, the effect of which in various circuit permutations and combinations is to be measured and tested.

Still another object of my invention is to provide a construction of a resilient link member and support for electrical components arranged to interchangeably bridge terminal posts of a test board for enabling quick replacement of the electrical component for building up an electrical network system.

Other and further objects of my invention reside in quick detachable and replaceable electrical connectors as set forth more fully in the specification hereinafter following by reference to the accompanying drawings in which:

Figure 1 is a side elevational view of one of the devices of my invention mounted in position on the terminals of a test board with parts of the device broken away and shown in section, the connector being provided with a compression coil spring for insuring good electrical connection between terminal posts; Fig. 2 is a view of a modified construction of connector embodying my invention by employing an expansion coil spring in lieu of the compression coil spring employed in the form of my invention shown in Fig. 1; Fig. 3 is a side elevational view of a further modified form of connector embodying my invention in which a flat strip-like spring member is employed in lieu of the coil springs shown in Figs. 1 and 2, parts of the connector being broken away and illustrated in section; Fig. 4 is a side elevational view showing the connector of my invention serving as a support and mounting means for a test lamp for ready attachment or detachment from the test board; Fig. 5 illustrates the application of the connector of my invention in association with a single throw single pole electric switch; Fig. 6 illustrates my invention applied to the mouting of an electrical resistance element on the test board; Fig. 7 illustrates the application of the connector and mounting means of my invention for the support of an electrical condenser; Fig. 8 illustrates a modified construction of link connector constructed in accordance with my invention, with special provision for bridging intermediate cross links employed on the test board, the view being taken on line 8-8 of Fig. 9; Fig. 9 is a fragmentary plan view of the arrangement shown in Fig. 8; Fig. 10 is a transverse sectional view taken on line I0-l0 of Fig. 8; Fig. 11 illustrates the application of th connector of my invention for attachably and detachabl mounting a double throw single pole electric switch with respect to the test board; Fig. 12 is a plan view of the construction of switch illustrated in Fig. 11; Fig. 13 is a side elevational view showing a solenoid device supported by the electrical connector of my invention in quick replaceable position on the test board; Fig. 14 is an end view of the solenoid device, looking approximately in the direction of line l4'l4 of Fig. 13; Fig. 15 is a transverse sectional view, taken on line I5|5 of Fig. 13; Fig. 16 illustrates in top plan view the connector of my invention applied to the mounting of a buzzer for quick attachment and detachment with respect to the test board; Fig. 17 is a bottom plan view showing the connector of my invention associated with the buzzer of Fig. 16; Fig. 18 is a side elevational view of the electrical connector and buzzer arrangement of my invention; Fig. 19 is a schematic and diagrammatic view of one form of test circuit in which electrical components constructed in accordance with my invention may be arranged; Fig. 20 illustrates a modified arrangement of test circuit utilized in connection with the circuit components of my invention; Fig. 21 shows a further modified form of test circuit employed in association with the electrical components of my invention; and Fig. 22 is a schematic crosssectional view showing the manner of establishing connection between the test leads which extend to the circuit components of my invention and the test circuit used for purposes of measurement of the various circuit components.

amaeee Referring to the drawings in detail, reference character I designates the test board, having pin terminals projecting therefrom at spaced intervals. I have represented two of such terminals by reference characters 2 and 3. The electrical connectors, which serve to interconnect the pin terminals, are constructed in such manner that good electrical connection is assured at all times between the pin terminals even though the electrical connection may be very quickly established. The electrical connector shown in Fig. 1 includes a pair of round rod members 4 and 1, each of which have a length substantially less than onehalf the distance between the'pin terminals. The rod members 4 and I each have flattened end portions illustrated at and 8 respectively. The flattened end portions 5 and 3 are each apertured as represented at 6 and 8 respectively, the apertures being of a size enlarged to approximately one and one-half times the diameter of the associated terminal pin 2 or 3. This permits the connector embodying the rod members 4 and 5 to be readily slipped over and removed from the ends of pins 2 and 3. The rod members 4 and I are interconnected by means of a compression coil spring illustrated at I0, having a diameter sufficiently large to readily embrace the round rod members 4 and 5 and having a length suflicient to extend over approximately one-quarter of the length of each of the rod members 4 and l, bridging the gap between the aligned ends of the rod members as shown, while maintaining spacial relation between the convolutions of the coil spring as shown at Ill suiflcient to assure continuous tension of the connecting link between the terminal pins. The ends of the compression coil spring III are soldered at H and I2 to the rod members 4 and 1 providing a good electrical and mechanical connection therewith. compression coil spring It thus tends to draw rod members 4 and 1 toward each other, estab- The lishing frictional connection between inner-face In of aperture 6 of rod member 4 and inner face 3a of aperture 9 of rod member I. In applying the connector to pin terminals 2 and 3, the rod members 4 and I are stretched apart sufliciently to allowthe apertures 6 and 9 to be readily engaged over the pins 2 and 3 and permit the compression coil spring Hi to draw the rod members 4 and 1 toward each other for maintaining frictional contact between faces 60, and 9a and the sides of pins 2 and 3. In removing the connector, the members 4 and 1 are stretched apart sufliciently to release the flattened ends 5 and 8 from engagement with the pins 2 and 3 to allow quick detachment thereof.

In Fig. 2 I have shown a similar construction of electrical connector embodying my invention except that I employ in this form of my invention an expansion coil spring |4 so that the friction contact between the apertured portions 3 and 9 of the connector is established between faces 6b and 3b of the apertures 6 and 9 and the inner faces of pins 2 and 3. In applying this type of connector to the pins 2 and 3, I compress the rod members 4 and I toward each other sufficient to slip the apertured ends of the rod members 4 and I over the pins 2 and 3 so that face 3b of rod member 4 engages pin terminal 2 and face 912 of rod member I engages pin terminal-3. In removing the connector, the same process is employed in that the rod members 4 and I are compressed toward each other to release the grictioial grip between faces 6b and 9b and pins and operative position is approximately one-half the distance between the pins 2 and 3. The flat lug members are apertured as represented at l3 and 2| to engage the pin terminals 2 and 3. As illustrated the ribbon-like spring I5 is of the compression type and mechanical and electrical connection is established between face IBa of aperture l8 and the side of pin 2 and bottom face 2|a of aperture 2| and the side of 'pin 3. The ribbonlike spring l5 may be of the expansion type in which event frictional engagement would be established between the face |8b of lug l6 and pin 2 and face 2|b of lug l9 and pin 3.

In Fig. 4 I have shown the connector of my invention applied as a supporting means for an electric test lamp illustrated at 22. Test lamp 22 is carried by screw threaded socket 23, the shell of which is connected by lug 24 to the short rod member 25 through soldered connection 26. 1

The inner contact of shell 23 passes through insulated plate. 21 and connects to strip 28 which is soldered at 29 to rod member 33. Rod member 30 is apertured at 3| to fit over pin 3 and establish electrical and mechanical connection therewith through the face represented at 3|a. The short rod member 25 is electrically and mechanically connected through coil spring 32 with the short rod member 33 which terminates in flattened lug 34. The flattened lug 34 is apertured at 35 to fit over pin terminal 2' and establish electrical connection therewith through face 35a. The coil spring 32 is of the compression type connected by solder 36 at one end to the rod member 25 and by solder 31 at the other end with short rod member 33. The short rod members 33 and 25 are spacially related and separated by a gap between the ends thereof which is bridged by the compression coil spring 32 in such manner that convolutions of coil spring 32 are spacially related to maintain the linkage under tension between pins 2 and 3 when the component such as the lamp 22 is mounted in position between the pins 2 and 3. In this arrangement an extension type spring may also be employed and the principles illustrated at- Fig. 2 applied to the component mounting shown in Fig. 4.

In Fig. 5 I have shown the manner of mounting a single pole single throw switch 38 with respect to the linkage of my invention. In this arrangement the same resilient linkage comprising coil spring 32 is employed and connected with a short member which corresponds to the short rod member 25 in Fig. 4. The short member in Fig. 5, however, is constituted by a rod member 39 which is flattened at 40 and provides a connection to insulated panel 4| through a rivet or other suitable connecting means 42. The opposite end of the insulated panel member 4| is connected through rivet or other suitable connecting means 43 with the lug member 44. Lug member 44 is apertured at 45 to engage pin terminal 33. The inner face 45a of ing 44 embraces the pin 3 for establishing mechanical and electrical connection therewith. The panel 4| provides a pivotal mounting means at 46 for the switch arm 41 which connects at 42 with flattened portion 40 of rod member 39. The switch arm 41 includes an upstruck portion 49 for imparting resiliency thereto and an operating handle 49 by which the switch arm 41may be moved into and out of electrical connection with the contact 59. Contact 59 connects through the rivet or other suitable connection 43 with the lug 44. A solder connection indicated generally by the deposit of solder 5| on lug.

44 is made through a suitable wire connection with the contact 59. The resilient link when placed in position upon pin terminals 2 and 3 may therefore provide for the quick opening and closing of the electrical circuit through the link by slight angular movement of switch arm 41.

In Fig. 6 I have shown the linkage of my invention applied to the mounting and support of an electrical resistor. In this arrangement an insulated panel 4| is supported between the flat end 49 of lug 39 and the flat end of lug 44 by suitable rivet connections indicated at 42 and43. Insulated panel 4| serves as a mounting means for the resistor 52 having leads 53 and 54 extending therefrom. Lead 53 is soldered at 55 to rod member 39 while lead 54 is soldered at 5| to lug 44, thus forming a series resistance path through the flexible link interconnecting pin terminals 2 and 3. I

In Fig. 7 I have shown an arrangement of resilient link similar to that shown in Fig. 6 except that an electrical condenser 56 is mounted on insulated panel 4| with lead 51 extending from one end and soldered at 55 to rod member 39 and lead 59 extending from the other end thereof and soldered to lug 44 at 5|. The resilient link when placed in position between pins 2 and 3 thus includes an electrical condenser in series circuit Path.

In Fig. 8 I have shown an extension of the test board including in addition to pin terminals 2 and 3 the spaced terminals 59, 69, 6|, 62, 63 and 54. Various combinations of electrical components can be assembled on these pin terminals as represented, for example, by the bridging connector shown at 95 in Fig. 8 and the continuous transverse connector 69 single pole single throw switch connector 61 in Fig. 9. The bridging connector 65 shown in Fig. 8 includes a rod portion 33. arranged similarly to the correspondingly numbered rod portion explained in Figs. 4-'! engageable through aperture 35 with pin member 2, and connected through coil spring 32 with the aligned end 69 of the bridging connector 95. A solder connection indicated at 69 is established between the aligned end 99 of bridging connector 95 and coil spring 32 as indicated. A loop 19 formed in bridging connector 65 extends over the transverse connector 66 as shown in Fig. 8 and connects with pin terminal 59. Aperture 1| in the flattened end 12 of bridging connector 65 fits over pin 59 and forms an electrical connection therewith. Fig. 8 illustrates in end section the transverse linkages 66 and 61 shown in plan view in Fig. 9. It will be observed that by reason of loop 19 of bridging connector 65, connection is made between pin terminals 2 and 59 without connection with transverse linkage shown at 99. The transverse link 61 including single pole single throw switch 41 provides means for continuing the circuit from bridging connector 65 to terminal pin 63.

In Figs. 11 and 12 I have shown the application of a single pole double throw switch to the replaceable linkage of my invention. In this arrangement the same tensioning means is provided as that in connection with Figs. 4-7 and an 6 insulated panel comparable to panel 4| is provided as represented at 13 somewhat longer than the insulated panel 4|. The single pole double throw switch arm 14 is pivoted at 15 on insulated panel 13 and is movable under control of insulated handle 16 to establish contact either with contact 11 or 19 depending upon the direction in which the switch arm is moved. The switch arm 14 pivoted at 15 is connected through flexible conductor 19 which may be extended to any suitable point on the test board and connected through a quick detachable connection with any of the other terminal pins which may form a terminal connection for a network arranged on the test board- Contact 11 connects through suitable rivet or other connector 42 to the lug 49 of the short rod member 39 while contact 19 connects through suitable rivet or other connector 43 with flat lug member 44in a manner similar to that explained in connection with Figs. 5-7. Thus a circuit may be established in a series path either through pin terminal 2 or pin terminal 3 extending through conductor 19.

In Figs. 1315 I have shown a form of the connector of my invention applied as a support for a solenoid for the education of the student in studying the operation of a solenoid. An electrical circuit may be laid out on the test board between various pin terminals. An insulated panel 99 is provided from one end of which a lug 9| projects for engaging by means of aperture 82 therein the pin terminal 3. The opposite end of the insulated panel 99 is apertured at 93 for the passage of the slidable lug member 94. A plate member is secured'over one edge of the insulated panel 99 and is apertured in a position conforming with the apertured portion 83 of panel 99 to allow passage of rod member 84 through both the plate and aperture 93. The rod member 84 has an enlarged flattened end 99 thereon which is apertured at 81 to engage pin terminal 2 and also serves as an abutment for coil spring 88 which is positioned between the flattened elongated end 86 and the plate 85 at the end of panel 99. The end of rod member 84 passes through the aperture 93 in panel 89 and terminates in the space 89 formed by a transverse aperture through panel 99. Rod member 94 is flattened at its end as shown at 99 forming an obstruction restricting the movement of the rod member 94 out of panel 99 beyond a predetermined distance sufilcient for the apertures and 81 in rod members 9| and 94 to be engaged over or removed from pin terminals 2 and 3. Rod member 84 is displaceable longitudinally of panel 99 under control of spring 99 which tends to continuously eject rod member 94. The panel 99 provides a mounting means for vertically arranged solenoid shown at 92, one end of which is electrically connected with the plate member 95 through lead 93 and thus connected through spring 68 with rod member 84 for establishing connection with pin terminal 2 and the other end through lead 94 with the rod member 9| for establishing connection with pin terminal 3. Solenoid 92 is provided with a vertically extending guide member 95 in the form of a tube longitudinally cut away at 96 to allow visual observation of the movement of armature 91 under conditions of energization of solenoid 92. The armature 91 is mounted for vertical movement within the guide formed by tubular member 95 and is suspended by coil spring 99 connected by means such as transverse rivet member 99 to the upper end of the tubular member 95. Thus the 75 student is able to observe the movement of the armature as the solenoid winding 92 is energized in the test circuit from time to time.

In Figs. 16, 7 and 18, I have shown a further electriccirc t component consisting of an electric buzzer and method of mounting the same with 'respectto the terminal posts of the test board. The buzzer is mounted upon a base I and is illustrated as including electromagnets IOI for operating the make and break armature system which is housed within the casing I02. On the base of the buzzer I arrange the insulated panel 80 with lug 8| extending from one end thereof and terminating in the flattened eyelet apertured at 82 and provided with the yieldably mounted rod member 04 extending through the aperture 82 in insulated panel 80 and yieldable under control of spring 88 as explained in connection with Figs. 13-15. The flattened end rod member'84 apertured at 81 is engageable with the terminal pins of the test board I as represented, for example, by the mounting of the buzzer over the pin terminals 2 and 3 as shown in Fig. 16. The 'rod member 84 is restricted in its output movement by the enlarged end 90 thereof which is visible through aperture 89 in panel 80. The movement of rod member 84, however, isadequate to allow the buzzer to be readily positioned on the test board with the apertured flattened ends of the rod members 8| and 84 engaged over the, pin terminals shown at 2 and 3. It will be realized that other forms of electrical components may be similarly mounted with adjustable contact members associated therewith for engagement with the terminal pins of the test board.

In Fig. 19 I have illustrated one manner in which the electrical connectors and mounting means for electrical components are used in association with a test circuit. The test circuit is shown as including a meter I03 having windings arranged for the precision measurement of volts, ohms and/or amperes with the circuits to the meterextending from binding posts I04, and I to an external control circuit from which leads are taken from socket terminals I06 and I01 to test leads which extend to the test board I. The external control circuit connected with meter I03 includes two control switches, one of which has been indicated at I08 and another of which is shown at I09. Each control switch has three separate positions indicated at I, 2' and 3' and I", 2 and 3", respectively. Control switch I06 provides means for selecting a path through contact 2' directly to binding post I06 (negative) or through contact 3, fuse III and series resistance II2 to the binding post I04 of meter I03. Switch I09 provides means for establishing a shunt path through contact 2' and resistance I I4 or a series path through contact I" and the potential source IIO of, for example 4 volts, from binding post I04 of meter I03. A 2% ampere test lamp H5 is provided in circuit with binding post I05 of meter I03 and binding post I01 (positive) leading to the test circuit. Intermediate the binding post I06 and binding post I04, of meter I03, I provide the potential source IIO, regulating resistance H6 and the adjustable resistance H1. The meter I03 is normally calibrated over a range of 0-300 milliamperes.

With switches I08 and I09 on contacts I and I" respectively, the circuit is available for measuring resistance in ohms over a range of 020,000 ohms.

With switches I08 and I09 in positions 2' and 2", the circuit is in condition to measure current in amperes over a range of 0-2 amperes.

With switches I08 and I09 in positions 3' and 3", respectively, the circuit is in a condition to measure volts over a range of 0-6 volts. The terminals I06 and I01 are illustrated more clearly in Fig. 22 as comprising a socket-like member II8 having a screw threaded shank II9 which passes through the insulated supporting panel represented at I20 and is secured in position with respect thereto through washer members I2I and I22 and securing nut member I23 which serves as a means for clamping and establishing electrical connection with conductor I24 leading to the meter circuit. The socket member H8 is longitudinally split for rendering the socket suificiently resilient to receive and grip the terminal tip I25 of the test lead I26. A similar terminal test lead is provided in association with binding post I01 as represented at I21. The test leads I26 and I21 are flexible and have a sufiicient length to permit the test leads to reach all positions on the test board I and to allow the alligator-like terminal gripping means represented at I28 and I29 to engage the terminal posts in any desired position throughout the test board. This permits an electrical network representing various electrical problems to be set up on the test board and measurements made of the circuit characteristics through such electrical components as are arranged on the test board. In Fig. 19, for example, I have shown two link connectors constituted by electrical resistance of different values represented at I30 and I3I connected between terminal pins 2, 6| and 62 as shown. The circuit measurements are made in the particular example illustrated between terminal post 2 and 62 with resistances I30 and I3I in series.

Various problems may be set up on the test board as represented for example, in Figs. 20 and 21, and measurements of the characteristics of the test circuits made. In Fig. 20 an ammeter having a scale deflection of 0-1 ampere is represented at I32 with an associated volt-ohmmeter indicated at I33 calibrated to read 0-6 volts and 0-150 ohms. Terminal I34 of the ammeter I32 is connected directly to socket terminal I35 (positive). Terminal I36 of the volt-ohmmeter I33 is also connected to socket terminal I35. A selector switch I31 is provided having positions I', 2" and 3" for selectively connecting the meters in the test circuit. Switch I31 is connected to socket terminal I38 (negative) as shown. When switch I31 is in position I', a circuit through an adjustable rheostat I39 and potential source I40 (1 volts) to terminal I4I of voltohmmeter I33. When switch I31 is in position 2" a circuit is completed through the 2% ampere pilot lamp I42 with terminal I43 of ammeter I42. When switch I31 is moved to position 3' a series resistance IE4 is connected in series with terminal I4I of volt-ohmmeter I33. Thus current voltage and resistance may be measured by applying the test leads I26 and I21 carrying connectors I29 and I28 thereon to selected terminal pins of the test board between which components of the test circuit are arranged as represented, for example, by resistance I30 connected between terminal pins 2 and BI and inductance 92 representative of solenoid winding 92 of the device represented in Figs. 13-15, connected to the pin terminals BI and I45. Thus various networks may be set up on the test board and measurements taken of diiferent portions thereof by means of the meter circuit shown.

In Fig. 21 I have shown an arrangement of is completed to the volt-ohmmetermeasuring circuit in which the ammeter remains continuously in the test circuit. I have shown the ammeter I32 withterminal I43 thereof connected to an auxiliary circuit which is supplied with current from source of potential I46 connected between terminals I41 and I48. Terminal I46 connects to bus bar I49 terminating in socket terminal I50. Terminal I34 of ammeter I32 connects through 2% ampere test lamp I42 with socket terminal II. The volt-ohmmeter is a combination instrument represented at I52 having terminal I53 connected with the socket terminal I 54 (positive). Terminal I55 of meter I52 is connected through series resistance I56 with contact I of switch I51 while contact 2" connects through battery source I58 and adjustable rheostat I59 directly to terminal I55 of meter I52.

SQwitch system I51 connectsjo socket terminal 160 (negative). The terminal pins insertable into the socket terminals and connected through the flexible test leads I26 and I21 may be plugged into the pair of socket terminals I60 and I54 for enabling the connectors I28 and I29 to be engaged upon pin terminals on the test board for the measurement of any selected network as represented, for example, by resistor I30 between pin terminals 2 and GI, resistor I6I between pin terminals 6| and I45, and test lamp 22 between pin terminals I45 and I62. The test prods may be connected to various parts of a test network and measurements taken on the meters when the pin connections are inserted in the socket terminals I54 and I60 of the measuring system. Resilient link connectors I63 and I64 interconnect the power source I46 with the network on the test board.

While I have explained my invention in certain of its preferred embodiments, I desire that it be 1 understood that no limitations are intended upon my invention and that modifications and changes may be made in carrying out details of my invention within the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows: 1. In an educational apparatus, an insulated test board carrying a multiplicity of projecting studs linearly spaced in two directions, said studs comprising pairs of electrical circuit terminals, connector means attachable to and removable from the circuit terminals, an intermediate connector means, a resilient connection between one of said first mentioned connector means and said intermediate connector means, and an apparatus unit suspended between said intermediate connector means and the other of said first mentioned connector means for establishing a series electrical path through said apparatus unit between said circuit terminals on said test board.

2. In an educational apparatus a test board formed from insulation material and having a plurality of conductive studs distributed in spaced positions over the surface thereof, said studs comprising pairs of electrical circuit terminals, connector means attachable to and detachable from said circuit terminals, an intermediate connector means aligned with the aforesaid connector means, an insulated panel member extending between one end of said intermediate connector means and one of said attachable and detachable connector means, a yieldable connection between the other end of said intermediate connector means and the other of said attachable and detachable connector means, and an apparatus unit carried by said insulated panel member and electrically included in circuit between said circuit terminals for establishing various circuit permutations and combinations on said test board.

3. In an educational apparatus, a test board formed from insulation material having a plurality of conductive studs distributed in spaced positions over the surface thereof, said studs comprising pairs of electrical circuit terminals, connector means attachable to and detachable from said circuit terminals, an intermediate connector means aligned with the aforesaid connector means, a panel of insulation material interposed between one end of one of said connector means and one end of said intermediate connector means, a tensioned connection between the other end of said intermediate connector means and the other of said connector means, and an electrical switch carried by said panel for opening the circuit through said connector while said connector remains in tensioned position between said circuit terminals for establishing various circuit permutations and combinations on said test board.

4. In an educational apparatus, a test board formed from insulation material having a plurality of conductive studs distributed in spaced positions over the surface thereof, said studs comprising pairs of electrical circuit terminals, connector means attachable to and detachable from said circuit terminals, an intermediate connector means aligned with the aforesaid connector means, a panel of insulation material interposed between one end of one of said connector means and one end of said intermediate connector means, an expansive connection between the other end of said intermediate connector means and the other of said connector means, and an electrical switch carried by said panel for opening the circuit through said connector while said connector remains in fixed mechanical position between said circuit terminals for establishing various circuit permutations and combinations on said test board.

5. In an educational apparatus, a test board formed from insulation material having a plurality of conductive studs distributed in spaced positions over the surface thereof, said studs comprising pairs of spacially related electrical circuit terminals, connector means attachable to and disconnectible from said circuit terminals, said connector means each having a length less than one-half the distance between said circuit terminals, and a coil spring interconnecting the adjacent ends of said connector means and stretchable between the adjacent ends thereof, said coil spring tending to maintain said connector means in mechanical and electrical engagement with said circuit terminals for maintaining a continuous electrical path through said connector means for establishing various circuit permutations and combinations on said test board.

6. In an educational apparatus, a test board formed from insulation material having a plurality of conductive studs distributed in spaced positions over the surface thereof, said studs comprising pairs of electrical circuit terminals, connector means attachable to and detachable from said circuit terminals, an intermediate connector means aligned with the aforesaid connector means, a panel of insulation material interposed between one end of one of said connector means and one end of said intermediate connector means, an expansive connection between the other end of said intermediate connector means 11 and the other of said connector means, a double throw electrical switch carried by saidpanel for selectively modifying the circuit through said connector while said connector'remainsl in fixed mechanical position between said circuit terminals to provide an electrical path through one or the other of said circuit terminals forestablishing various circuit permutations and combinations on said test board.

7. An electrical instruction board formed from i ulation material and having a multiplicity of s cially related electrical terminals thereon, and electrical connectors for longitudinally and transversely interconnecting. said electrical terminals, each of said connectors having yieldable means for tensioning the connectors between said terminals, one of said connectors having a loop therein for displacing the said connector out of the path of the other connector and maintaining the connectors in spacial relation with respect to each other for establishing various circuit permutations and combinations on said instruction board.

,8.'In an educational apparatus, a test board formed from insulation material and having a plurality of conductive studs distributed in spaced positions over the surface thereof, said studs comprising pairs of .electrical circuit terminals, an insulated panel member having a length substantially less than the distance between said circuit terminals, a lug member extending from one end of said insulated panel member and attachable and detachable with respect to one of said electrical circuit terminals, a lug yieldably projectible from the opposite end of said insulated panel and attachable to and detachable from the other of said electrical circuit terminals, an apparatus unit carried by said insulated panel, and electrical connections between said apparatus unit and each of said lug members whereby said apparatus unit is electrically connected with said circuit terminals and maintained in tensioned connection therewith for establishing various circuit permutations and combinations on said test board.

9. In an educational apparatus, a test board formed from insulation material having a plurality of conductive studs distributed in spaced positions over the surface thereof. said studs comprising pairs or electrical circuit terminals, an insulated panel.member having a length substantially less than the distance between said circuit terminals, a lug member extending from 1g one end of said insulated panel member and attachable and detachable with respect to one of said electrical circuit terminals, a lug yieldably projectible from the opposite end of said insulated panel and attachable to and detachable from the other of said electrical circuit terminals. a solenoid mounted on said insulated panel with its axis extending substantially normal to the plane of said panel, an armature member reciprocative by said solenoid, and electrical connections between opposite ends of said solenoid andsaid lug members whereby said solenoid is electrically connected with said circuit terminals and maintained in tensioned electrical connection therewith for establishing various circuit permutations and combinations on said test board.

10. Electrical apparatus comprising a substan-. tially planar base of nonconducting material; a series of studs of conducting material affixed to said base in equally spaced parallel rows, the' distance between studs in a row being the same as the distance between rows, and said studs projecting from said base at right angles; a series of conductors connecting certain of said studs to form an electrical circuit, each said conductor comprising a substantially rigid but extensible element having an eyelet at each end and of such length that it must be slightly stretched in order to slip the eyelets over a pair of said adjacent studs and make a good electrical contact therewith; said studs being of sufficient height to accommodate several of said eyelets, and means for connecting said circuit to a source of electrical energy.

ARDEN E. ROANE.

REFERENCES CITED The following references are of record in the file of this patent: 

